SIGMA 28-70mm F2.8
DG DN | Contemporary

To increase stability, this lens configuration uses movable internal lens elements that adjust focus without changing the length of the lens barrel.

The lens is capable of smooth, quiet and high-speed AF made possible by a stepping motor, as well as supports Face/Eye Detection AF and video AF.

The super multi-layer coating is combined with SIGMA's unique coating technology "NPC (Nano Porous Coating)". The lens has been designed to be less susceptible to strong incident light such as backlight.
"NPC (Nano Porous Coating)" incorporates porous silica as the coating material. The porous silica layer has nano-sized holes with air inside. Having holes of this size enables a large reduction in the refractive index, allowing the reflectance to be lowered more than conventional anti-reflective coatings. As a result, reflected light causing flares and ghosting is sharply reduced, achieving clear image quality.

SIGMA's own Super Multi-Layer Coating suppresses flare and ghosting by preventing reflections with in the lens. All lenses in the current SIGMA range feature this original technology. In digital cameras, flare and ghosting may also be caused by reflections between the image sensor and lens surfaces. Here too, SIGMA's Super Multi-Layer Coating is highly ef fective, assuring images of outstanding contrast.

Incorporates a water and oil-repellent coating that allows water to be wiped away easily and prevents oil and fat from sticking to the surface, even in challenging shooting conditions. At the same time, the maintenance of the lens surface becomes easier.

Using this swich, it is possible to switch the focus mode between AF and MF.

A focus movement method of interchangeable lenses for mirrorless cameras (DN lens) in relation to the rotational angle of the focus ring during manual focusing.
With "non-linear focus," the amount of focal point movement varies depending on the focus ring rotational speed.
With linear focus, if the focus ring rotational angle is the same, the amount of focal point movement remains the same regardless of the focus ring rotational speed.

The lens mount incorporates rubber sealing to protect the mount from dust and water drops.

The brass mount combines high precision with rugged construction. Its treated surfaces and enhanced strength contribute to the exceptional durability of the lens.

The polygonal shape of a conventional iris dia phragm causes out-of-focus light points to appear polygonal. A rounded diaphragm is designed to pro duce rounded out-of-focus light points when opened to near maximum aperture. This creates attractive bokeh effects in many situations, such as when pho tographing a subject against an out-of-focus surface of water from which light is being reflected.

The degree to which light is refracted by glass depends on the light's wavelength. This fact causes different colors of light to focus at slightly different points. The result is chromatic aberration, the color fringing that is particularly noticeable in telephoto lenses. Most chromatic aberration can be removed by combining a high-refractivity convex lens element with a low-refractivity concave element. Yet residual chromatic aberration known as "secondary spectrum" may still remain. To minimize this secondary spectrum, which can be a serious issue with conventional lenses, SIGMA lenses feature up to three types of exclusive low-dispersion glass offering superior performance: ELD (Extraordinary Low Dispersion), SLD (Special Low Dispersion) and FLD ("F" Low Dispersion). In particular, FLD glass offers ultra-low dispersion in combination with high transmittance and the anomalous dispersion characteristics of fluorite. Meticulous deployment of these types of exclusive low-dispersion glass and optimization of power distribution gives SIGMA lenses superlative image rendition undiminished by residual chromatic aberration.